Fast surface approximation for volume and surface area measurements using distance transform

The laser triangulation technique has been widely used to obtain three-dimensional (3-D) information because of its accuracy. It is a fast, noncontact method for 3-D measurement. However, 3-D data obtained from triangulation are not dense and usually not complete for surface reconstruction, especially for objects with irregular shapes. As the result of fitting surfaces with these sparse 3-D data, inaccuracy in measuring object surface area and volume is inevitable. Accurate sur- face reconstruction from incomplete 3-D data points becomes an impor- tant step toward accurate noncontact surface area and volume measure- ments of objects moving at high speed. A novel computer vision technique combining laser triangulation and a distance transform is de- veloped to improve the 3-D measurement accuracy for objects with ir- regular shapes. The 2-D object image boundary points combined with the 3-D data obtained from laser triangulation are used to generate a 3-D wire frame. The distances from each pixel within the object boundary to its nearest boundary point are then used as the constraints for surface approximation. With this additional information from the distance trans- form, more accurate surface approximation can be achieved. This novel surface approximation technique is implemented and the measurement accuracy is compared with the accuracy using other surface interpolation techniques for the volume measurement of moving objects. © 2003 Soci-